Apparatus and Methods for Relay-Assisted Uplink Communication

ABSTRACT

A terminal device is arranged to communicate with a base station via a relay device in a wireless communications system. The terminal device comprises: a transmitter arranged to transmit an access request message to the base station, wherein the access request message comprises one from a set of access preambles that indicate relay device uplink assistance is required; a receiver arranged to receive an access request grant response from the base station; and a control processor operably coupled to the transmitter and receiver and arranged to: process the access request grant response and determine from a timing advance part thereof transmit power control (TPC) information for transmitting to the base station via the relay device.

FIELD OF THE INVENTION

The field of this invention relates to methods and apparatus forrelay-assisted uplink communication.

BACKGROUND OF THE INVENTION

A recent development in third generation (3G) wireless communications isthe long term evolution (LTE) cellular communication standard, sometimesreferred to as 4^(th) generation (4G) systems. Both of thesetechnologies are compliant with third generation partnership project(3GPP™) standards. It is anticipated that 4G systems will be deployed inexisting spectral allocations owned by Network Operators and newspectral allocations that are yet to be licensed. Irrespective ofwhether these LTE spectral allocations use existing second generation(2G) or 3G allocations being re-farmed for fourth generation (4G)systems, or new spectral allocations for existing mobile communications,they will be primarily paired spectrum for frequency division duplex(FDD) operation.

In addition to the large number of standard wireless subscribercommunication units that employ the above technologies, there is anincreasing number of other communication devices that may usefullyconnect to current mobile telecommunication networks. Examples includeso-called machine type communication (MTC) devices, which are typifiedby semi-autonomous or autonomous wireless communication units that aredesigned to communicate small amounts of data on a relatively infrequentbasis. Examples of MTC devices include so-called smart meters, which,for example, may be located in a customer's house and periodicallytransmit information back to a central MTC server data relating to thecustomers consumption of a utility such as gas, water, electricity, andso on. Thus, a large number of MTC devices are expected to support verylow power consumption and with small, intermittent data transmissions.

It is also known that ‘uplink-only relaying’ is a network topology thatmay be used to address the issue of achieving low transmit power inlow-cost MTC devices, for instance, in macro cellular LTE networks. Ingeneral, in relay-node applications, there is typically sufficientsystem gain on the downlink (base station to subscriber communicationunit or terminal device) to support MTC devices (or User Equipment UE)(MTC-UE) at the cell edge of the macrocell of the eNodeB (eNB). However,with the low output power of the MTC devices the uplink (terminal deviceto base station) system gain is significantly reduced compared with thedownlink. The use of a single hop uplink-only relay device (MTC-RN) canbe used to address this issue and close the link budget for MTC-UE. Asingle hop may be assumed, provided that the MTC-RN can be expected tohave similar characteristics to an LTE UE. In a network where relaydevices (also referred to herein as relay devices) are utilised to relayuplink data from the terminal devices to the eNodeB, the eNodeB may bereferred to as a donor eNodeB (DeNB).

FIG. 1 illustrates a simplified schematic of an uplink-only single-hoprelay communication system 100, comprising base station (such as eNodeB)105, carrier network 110, relay device 115 and user equipment (UE) 120.In this simplified schematic, eNodeB 105 communicates with other eNodeBs(not shown) via the carrier network 110. Communication system 100comprises an asymmetric uplink/downlink arrangement, whereby wirelessdownlink communications between the base station 105 and UE 120 have adirect communication path 125, but are single-hopped for the uplinkcommunication path 130 from UE 120 to base station 105 via relay device115. The base station 110 may also transmit control signalling on aseparate downlink path 135 to relay device 115 in order to control theoperation of the relay device 115.

The configuration of FIG. 1 allows lower power transmissions to be sentfrom the UE 120, for example where the lower power is sufficient for theMTC device's lower transmit power to be able to reach the relay device'sreceiver at a decodeable power level, whereas the MTC device's lowertransmit power would not be able to reach the eNodeB's receiver at adecodeable power level. However, the disadvantage with this system isthat the transmission time from the UE 120 to the base station 110 hasbeen increased due to the implementation of relay device 115. Further,there is no transmission from the relay device 115 to the UE 120.Therefore, a potential problem with uplink-only relaying is that therelay device is unable to feed back control information to the MTCdevice to support efficient future transmissions between the MTC deviceand the base station via the relay device, for example to control thepower of such transmissions to avoid interference with other users.

Therefore there is a need for a terminal device and a base stationsupporting an uplink-only relaying system to be able to better controlcommunications between the terminal device, such as an MTC device, andthe base station, such as an eNodeB.

SUMMARY OF THE INVENTION

The present invention provides communication units and methods ofoperation at such communication units in a communication system thatsupports a terminal device communicating with a base station via a relaydevice, as described in the accompanying claims. Specific embodiments ofthe invention are set forth in the dependent claims. These and otheraspects of the invention will be apparent from and elucidated withreference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a simplified schematic of an uplink-only single-hopcommunications system.

FIG. 2 illustrates a 3GPP™ LTE cellular communication system adapted inaccordance with some example embodiments of the present invention.

FIG. 3 illustrates an example block diagram of a terminal device, suchas a 3GPP™ LTE user equipment adapted in accordance with some exampleembodiments of the present invention.

FIG. 4 illustrates a simplified block diagram of random access preambletransmission.

FIG. 5 illustrates a simplified block diagram of a modified randomaccess preamble transmission.

FIG. 6 illustrates an example of a simplified block diagram of a furthermodified random access preamble transmission, according to an exampleembodiment of the invention.

FIG. 7 illustrates an example of an alternative simplified block diagramof a modified random access preamble transmission, according to anexample embodiment of the invention.

FIG. 8 illustrates an example of a simplified block diagram of a mediumaccess control (MAC) element, according to an example embodiment of theinvention.

FIG. 9 illustrates an example of a simplified block diagram of a randomaccess response (RAR) element, according to an example embodiment of theinvention.

FIG. 10 illustrates an example of a modified block diagram of a modifiedrandom access preamble transmission, according to an example embodimentof the invention.

FIG. 11 illustrates an example of both a prior art and modified randomaccess response RAR) element according to an example embodiment of theinvention.

FIG. 12 illustrates a further example of a modified random accessresponse RAR) element, according to an example embodiment of theinvention.

FIG. 13 illustrates a flow chart of a terminal device encompassingaspects of the invention.

FIG. 14 illustrates a flow chart of a relay device encompassing aspectsof the invention.

FIG. 15 illustrates a flow chart of a base station, such as an eNodeB,encompassing aspects of the invention.

FIG. 16 illustrates a simple example of a typical computing system thatmay be employed to implement signal processing functionality inembodiments of the invention

DETAILED DESCRIPTION

Referring now to FIG. 2, a wireless communication system 200 is shown inoutline, in accordance with one example embodiment of the invention. Inthis example embodiment, the wireless communication system 200 iscompliant with, and contains network elements capable of operating over,a universal mobile telecommunication system (UMTS™) air-interface. Inparticular, the embodiment relates to a system's architecture for anEvolved-UMTS Terrestrial Radio Access Network (E-UTRAN) wirelesscommunication system, which is currently under discussion in the thirdGeneration Partnership Project (3GPP™) specification for long termevolution (LTE), based around OFDMA (Orthogonal Frequency DivisionMultiple Access) in the downlink (DL) and SC-FDMA (Single CarrierFrequency Division Multiple Access) in the uplink (UL), as described inthe 3GPP™ TS 36.xxx series of specifications. Within LTE, both timedivision duplex (TDD) and frequency division duplex (FDD) modes aredefined.

The wireless communication system 200 architecture consists of radioaccess network (RAN) and core network (CN) elements 204, with the corenetwork elements 204 being coupled to external networks 202 (namedPacket Data Networks (PDNs)), such as the Internet or a corporatenetwork. The CN elements 204 comprise a packet data network gateway(P-GW) 207. In order to serve up local content, the P-GW may be coupledto a content provider 209. The P-GW 207 may be further coupled to apolicy control and rules function entity (PCRF) 297 and a Gateway 206.

The PCRF 297 is operable to control policy control decision making, aswell as for controlling the flow-based charging functionalities in apolicy control enforcement function PCEF (not shown) that may reside inthe P-GW 207. The PCRF 297 may further provide a quality of service(QoS) authorisation class identifier and bit rate information thatdictates how a certain data flow will be treated in the PCEF, andensures that this is in accordance with a UE's 225 subscription profile.

In example embodiments, the Gateway 206 may be a Serving Gateway (S-GW).The Gateway 206 is coupled to a mobility management entity MME 208 viaan S11 interface. The MME 208 is operable to manage session control ofGateway bearers and is operably coupled to a home subscriber service(HSS) database 230 that is arranged to store subscriber communicationunit 225 (user equipment (UE)) related information. As illustrated, theMME 208 also has a direct connection to each eNodeB 210, via an S1-MMEinterface.

The HSS database 230 may store UE subscription data such as QoS profilesand any access restrictions for roaming. The HSS database 230 may alsostore information relating to the P-GW 207 to which a UE 225 canconnect. For example, this data may be in the form of an access pointname (APN) or a packet data network (PDN) address. In addition, the HSSdatabase 230 may hold dynamic information relating to the identity ofthe MME 208 to which a UE 225 is currently connected or registered.

The MME 208 may be further operable to control protocols running betweenthe user equipment (UE) 225 and the CN elements 204, which are commonlyknown as Non-Access Stratum (NAS) protocols. The MME 208 may support atleast the following functions that can be classified as functionsrelating to bearer management (which may include the establishment,maintenance and release of bearers), functions relating to connectionmanagement (which may include the establishment of the connection andsecurity between the network and the UE 225) and functions relating tointer-working with other networks (which may include the handover ofvoice calls to legacy networks). The Gateway 206 predominantly acts as amobility anchor point and is capable of providing internet protocol (IP)multicast distribution of user plane data to eNodeBs 210. The Gateway206 may receive content via the P-GW 207 from one or more contentproviders 209 or via the external PDN 202. The MME 208 may be furthercoupled to an evolved serving mobile location center (E-SMLC) 298 and agateway mobile location center (GMLC) 299.

The E-SMLC 298 is operable to manage the overall coordination andscheduling of resources required to find the location of the UE that isattached to the RAN, in this example embodiment the E-UTRAN. The GMLC299 contains functionalities required to support location services(LCS). After performing an authorisation, it sends positioning requeststo the MME 208 and receives final location estimates.

The P-GW 207 is operable to determine IP address allocation for a UE225, as well as QoS enforcement and flow-based charging according torules received from the PCRF 297. The P-GW 207 is further operable tocontrol the filtering of downlink user IP packets into differentQoS-based bearers (not shown). The P-GW 207 may also serve as a mobilityanchor for inter-working with non-3GPP technologies such as CDMA2000 andWiMAX networks.

If the Gateway 206 comprises an S-GW, the eNodeBs 210 would be connectedto the S-GW 206 and the MME 208 directly. In this case, all UE packetswould be transferred through the S-GW 206, which may serve as a localmobility anchor for the data bearers when a UE 225 moves between eNodeBs210. The S-GW 206 is also capable of retaining information about thebearers when the UE 225 is in an idle state (known as EPS connectionmanagement IDLE), and temporarily buffers downlink data while the MME208 initiates paging of the UE 225 to re-establish the bearers. Inaddition, the S-GW 206 may perform some administrative functions in thevisited network, such as collecting information for charging (i.e. thevolume of data sent or received from the UE 225). The S-GW 206 mayfurther serve as a mobility anchor for inter-working with other 3GPP™technologies such as GPRS™ and UMTS™.

As illustrated, the CN 204 is operably connected to two eNodeBs 210,with their respective coverage zones or cells 285, 290 and a pluralityof UEs 225 receiving transmissions from the CN 204 via the eNodeBs 210.In accordance with example embodiments of the present invention, atleast one eNodeB 210 and at least one UE 225 (amongst other elements)have been adapted to support the concepts hereinafter described.

The main component of the RAN is an eNodeB (an evolved NodeB) 210, whichperforms many standard base station functions and is connected to the CN204 via an S1 interface and to the UEs 225 via a Uu interface. Awireless communication system will typically have a large number of suchinfrastructure elements where, for clarity purposes, only a limitednumber are shown in FIG. 2. The eNodeBs 210 control and manage the radioresource related functions for a plurality of wireless subscribercommunication units/terminals (or user equipment (UE) 225 in UMTS™nomenclature).

Each of the UEs 225 comprise a transceiver unit 227 operably coupled tocontrol processing logic 229 (with one UE illustrated in such detail forclarity purposes only). The system comprises many other UEs 225 andeNodeBs 210, which for clarity purposes are not shown.

As illustrated, each eNodeB 210 comprises one or more wirelesstransceiver (transmitter and/or receiver) unit(s) 294 that is/areoperably coupled to a control processor 296 and memory 292 for storing,inter alia, information relating to UEs and UE capabilities, for examplewhether the UE is able to or may be required to operate in an extendedcoverage mode via a relay device. Each eNodeB 210 further comprises ascheduler 291, which may be operably coupled to the one or more wirelesstransceiver unit(s) 294, the control processor 296 and memory 292.

In example embodiments of the present invention, a control processor ofa network element, such as control processor 296 of eNodeB 210, isarranged to transmit a signal to a wireless communication unit, such asUE 225, and receive communications back from the UE, either direct orvia a relay device.

Further, as illustrated, in some instances UEs 225 may be served byrelay devices 212. In this example embodiment, relay devices 212 areasynchronous relay devices, allowing information to, at least, berelayed from UEs 225 to eNodeBs 210, without necessarily providing thereverse communication link of forwarding communication from the eNodeBs210 to the UEs 225. In part, this relay device asynchronous mode ofoperation is a result of the transmit power and receiver sensitivity ofthe eNodeBs 210 being greater than the transmit power and receiversensitivity of the UEs 225. In this manner, the eNodeBs may transmitsignals on the downlink (DL) path to the UEs 225 located at the edge ofits communication coverage direct, whereas the UE's transmit power maybe insufficient to achieve the corresponding uplink (UL) communicationto the eNodeB.

Here, the asynchronous relay device 212 assists (i.e. relays) the ULcommunication from the UE 225 to the corresponding eNodeB 210. In thisexample embodiment, relay devices 212 comprise, at least, controlprocessor 213 operably coupled to a transceiver (not shown) and a memorydevice 214. In some examples, the control processor 213 may be locatedon an integrated circuit (not shown). In example embodiments, relaydevice 212 is configured to receive a wireless communication signal 220from UE 225 and selectively relay this wireless communication signal 216to eNodeB 210. In some instances, relay device 212 may receive wirelesscommunication signals 218 from eNodeB 210. In some example embodiments,relay devices 212 may modify a received wireless communication signal220 before relaying 216 to eNodeB 210. In other example embodiments,relay devices 212 may be controlled via eNodeB 210 via, say, wirelesscommunication signal 218, In yet further example embodiments, relaydevices 212 may be operable to determine information independently ofeNodeB 210.

In some examples of the invention, a base station (such as eNodeB 210)is arranged to communicate with a terminal device (such as UE 225) on anuplink channel via a relay device 212 in a wireless communicationssystem. The base station comprises: a receiver arranged to receive anaccess request message from the terminal device; and a control processoroperably coupled to the receiver and arranged to: process the accessrequest message; extract a relayed control element that indicates relaydevice uplink assistance was used wherein the relayed control elementcomprises a power delta from the relay device; and construct an accessrequest grant response message wherein the access request grant responsecomprises a larger field for power control and a comparable smallerfield for timing advance information for use in relayed communicationsas compared to corresponding size of fields for use in non-relayedcommunications; and transmit the access request grant response to theterminal device 225.

Clearly, the various components within the eNodeB 210, UE 225 and/orrelay device 212 can be realized in discrete or integrated componentform, with an ultimate structure therefore being an application-specificor design selection. Further, although example embodiments of theinvention have been described with reference to an evolved NodeB(eNodeB), UE 225 and relay device 212, it should be apparent to askilled person that example embodiments of the invention could beutilised with any base station (or other network element), terminaldevice or communication relay device.

Referring now to FIG. 3, a block diagram of a terminal device, such asUE 225 of FIG. 2 is shown, adapted in accordance with some exampleembodiments of the invention. The UE 225 contains an antenna 302 coupledto antenna switch 304 that provides isolation between receive andtransmit chains within the UE 225. One or more receiver chains, as knownin the art, include receiver front-end circuitry 306 (effectivelyproviding reception, filtering and intermediate or base-band frequencyconversion). The receiver front-end circuitry 306 is coupled to a userinterface 310, such as a display, touch screen or keypad via a signalprocessing module 308 (generally realised by a digital signal processor(DSP)). A skilled artisan will appreciate that the level of integrationof using receiver circuits or components may be, in some instances,implementation-dependent.

The control processor 213 maintains overall operational control of theUE 225. The control processor 213 is also coupled to the receiverfront-end circuitry 306 and the signal processing module 308. In someexamples, the control processor 213 is also coupled to a buffer module317 and a memory device 214 that selectively stores operating regimes,such as decoding/encoding functions, synchronization patterns, codesequences, and the like. A timer 318 is operably coupled to the controlprocessor 213 to control the timing of operations (transmission orreception of time-dependent signals) within the UE 225.

As regards the transmit chain, this essentially includestransmitter/modulation circuitry 322 and a power amplifier 324 operablycoupled to the antenna, antenna array 302, or plurality of antennae.

The transmitter/modulation circuitry 322 and the power amplifier 324 areoperationally responsive to the control processor 213.

In some examples of the invention, a terminal device (such as UE 225),for wirelessly communicating data to a base station (such as eNodeB 210)via a relay device 212 comprises: a transmitter arranged to transmit anaccess request message wherein the access request message comprises onefrom a set of access preambles that indicate relay device uplinkassistance is required; a receiver arranged to receive an access requestgrant response from the base station; and a control processor 213operably coupled to the transmitter and receiver and arranged to:process the access request grant response; and determine from a timingadvance part thereof transmit power control (TPC) information fortransmitting to the base station via the relay device.

The control processor 213 and/or signal processor module 308 in thetransmit chain may be implemented as distinct from the signal processorin the receive chain. Alternatively, a single processor may be used toimplement a processing of both transmit and receive signals, as shown inFIG. 3. Clearly, the various components within the UE 225 can berealized in discrete or integrated component form, with an ultimatestructure therefore being an application-specific or design selection.

As discussed above, a potential issue with an asynchronousrelay-assisted uplink is that the relay device is unable to communicatedirectly with the UE 225. An example of a possible problem with theabove topology is illustrated in FIG. 4.

FIG. 4 illustrates an example access sequence diagram 400 of a UE 410transmitting a series of preambles on a random access channel (RACH) toa base station at progressively higher power levels (i.e. the UEoperating in a power ramping mode). In general, the UE 410 randomlyselects a random access preamble from a group of predetermined randomaccess preambles available to it. The preamble is transmitted on a nextavailable Physical Random Access Channel (PRACH) resource available tothe UE 410. The position (in time and frequency resource) of thetransmitted random access preamble implicitly provides a temporaryidentifier, e.g. Random Access Radio Network Temporary Identifier(RA-RNTI), for the transmitting UE 410.

If the random access preamble is received at the base station (such aseNodeB 420), a random access response is transmitted from the eNodeB 420to the UE 410. The random access response is transmitted on the physicaldownlink shared channel (PDSCH), with the UE 410 being informed via anindication on the physical downlink control channel (PDCCH) of thedownlink resources on which the random access response is to be carried.In particular, the PDCCH has its cyclic redundancy check (CRC) bitsscrambled using the RA-RNTI (as derived from the time and frequencyresources utilised to transmit the random access preamble), and alsoindicates a resource block assignment (time and frequency resources) onthe PDSCH that will carry the random access response.

The UE 410 recognises that the random access response is intended for itby means of the CRC bits being scrambled by its RA-RNTI, and looks atthe assigned resource block in the PDSCH. The RAR also contains a randomaccess preamble identifier (RAPID), which is based on the actualpreamble used by the UE. This provides a further mechanism for the UE tobe able to identify the appropriate response (in addition to theRA-RNTI, based on time/frequency of the transmitted preamble). Inresponse to the random access response, the UE 410 transmits a message-3radio resource control (RRC) Connection Request Message to the eNodeB420. The message-3 is transmitted on physical uplink shared channel(PUSCH) resources allocated by the random access response. Once the RARis received, the RAPID indication may be used to distinguish betweenmultiple UEs that make preamble attempts.

In response to the message-3, the eNodeB 420 sends certain informationto the UE 410 for contention resolution purposes. This information istransmitted on the PDSCH (again on resources allocated by the PDCCHusing the temporary C-RNTI allocated in the RAR to address the UE, whichbecome the UEs permanent identifier if contention resolution issuccessful). The contention resolution information is contained within aUE Contention Resolution Identity control element. If the UE ContentionResolution Identity received at the terminal device/UE 410 from theeNodeB 420 matches a CCCH (Common Control Channel) SDU (Service DataUnit) transmitted in the message-3, then the UE 410 considers thatcontention resolution has been successful and that the random accessprocedure has been successfully completed.

The reason for providing contention resolution is that more than oneUE/terminal device may attempt to access the network using the samerandom access preamble on the same time and frequency resource. The CCCHSDUs transmitted by the contending UEs/terminal devices can be expectedto be different, and therefore UEs can determine if their random accessresponse is successful by comparing their transmitted CCH SDU with theone returned to them by the eNodeB 420 in the contention resolutionidentity medium access control (MAC) layer control element. Thiscontention resolution operation may be applied to all relevant exampleembodiments of the invention.

If a random access response/acknowledgement is not received by the UE410, it knows that the base station/eNodeB 420 did not receive the UE'stransmission and, thus, one or more successive random access preamble issent, in this example, with a different, higher power level.

As shown, in a relay assisted context, relay device (RN) 415 is locatedcloser to the UE 410 than the intended recipient eNodeB 420 and is thuspotentially able to assist the UE 410 in accessing the core network,should the UE 410 be located too far away from the base station/eNodeB420.

The simplified example diagram of random access preamble transmissions400, comprises a number of failed RACH preamble transmissions 425, 430,435, 440, a successful RACH preamble transmission 445 and a RACHresponse 450. As shown, the UE 410 transmits a succession of randomaccess preambles 425, 430, 435 and 440 utilising a power ramping regime,until the transmit power is hopefully strong enough to enable a RACHpreamble 445 to be detected by the eNodeB 420. Each RACH preambletransmission is randomly selected by the UE 410. As shown, the UE 410 islocated too far away from the base station/eNodeB 420 and therefore eachof the RACH preambles 425, 430, 435, 440 is received by the relay device415, but not by the eNodeB 420.

The relay device 415 is able to identify failed transmissions by notingthe received RACH preambles that do not have a corresponding RACHresponse from eNodeB 420, for example using the Random Access RadioNetwork Temporary Identifier (RA-RNTI). However, the relay device 415does not know that the failed RACH preambles have been transmitted fromthe same UE 410, since each selected RACH preamble is randomly selectedby the UE 410. Therefore the relay device 415 does not, in thisexplanatory diagram 400, know which UE 410 to assist with a RACH request(should a plurality of UEs be concurrently transmitting RACH requests).

In the case of the successfully transmitted and received RACH preamble445, the relay device 415 is able to receive a corresponding RACHresponse 450 from the eNodeB 420, signalling that the relay device 415is not required for further use by the UE 410, as anintermediary/relaying communication unit.

However, in this illustrated diagram, the relay device 415 is unable torelate any successful RACH preamble 445 with the failed RACH preambles425, 430, 435 and 440 to identify that it is not required to assist thefailed preambles, and, in the view of the relay device 415, there maystill be UEs within its vicinity that require assistance to communicatewith the core network. As each subsequent preamble re-transmission bythe UE 410 uses a completely new randomly selected RACH preamble, it isalmost impossible for the relay device 415 to determine whether twosubsequent preamble re-transmissions have originated from the same UE410.

FIG. 5 illustrates a simplified block diagram 500 of a modified randomaccess preamble transmission according to example embodiments of theinvention. The initial operation of this illustrated example is similarto that of FIG. 4, except that when the UE 510 reaches its maximumtransmit power in the power ramping mode of random access preambles 525,530, 535, and there has not been a corresponding RACH response from theeNodeB 520, a special group of RACH preambles 540 is utilised instead ofthe current group.

Transmitting the special group of RACH preambles 540 at the same power(for example at a maximum power) as the previous failed RACH preamble535 allows the relay device (relay node (RN)) 515 to determine that theoriginating UE 510 has failed to connect directly to the eNodeB 520. Inthis case, the relay device 515 then relays 545 the implied informationcontained in the random access preamble in a special MAC message. TheeNodeB 520 then transmits a corresponding RACH response 550 to the UE510.

In some instances, it is preferable for the UE 510 to transmit thespecial group of RACH preambles 540 at maximum power as it at leastguarantees that a connection can be made between the UE 510 and therelay device 515 quickly, in view of the fact that there may alreadyhave been an access delay due to the power ramping of the previousrandom access preambles 525, 530, 535. However, it may also be that theUE 510 is just out of coverage range of the eNodeB 520 to be able tosuccessfully transmit to the eNodeB 520, whereas it may actually belocated very close to the relay device 515.

This maximum transmit power transmission may be too high for the relaydevice 515 to successfully receive the special group of RACH preambles540, if for example, the UE 510 is very close to the relay device 515.Therefore, a potential problem with the aforementioned approach may bethat the relay node receiver is de-sensitized by the UE 510 transmittingthe special group of RACH preambles 540 at maximum power. In thisexample embodiment, the relay device 515 is unable to inform the UE 510that it is transmitting at too high a power, due to asymmetric nature ofthe communication (i.e. no downlink communication channel beingavailable from the relay device 515 to the UE 510. Therefore, in thiscase, there is a need for the relay device 515 to be able to control thepower of RACH transmissions transmitted from the UE 510 in arelay-assisted scenario when the UE is unable to access the core networkvia the eNodeB 520 direct.

Although the above example proposes the special group of RACH preambles540 being transmitted at a maximum power level, the problem may stilloccur if the transmission of the special group of RACH preambles 540 ismade at a level below the maximum transmit power of the previouslytransmitted RACH preambles 525, 530, 535.

FIG. 6 illustrates an example simplified block diagram 600 of a furthermodified random access preamble transmission. The operation is similarto that discussed with respect to FIG. 5. Therefore, only thedifferences between the operation of FIG. 6 and FIG. 5 will be discussedbelow.

The example simplified block diagram 600 of FIG. 6 further comprises amessage-3 transmission 655 from UE 610 to relay device 615 and a relayedmessage-3 transmission 660 sent from relay device 615 to eNodeB 620.Notably, in this example embodiment, the message-3 transmissioncomprises a radio resource control (RRC) connection request message. Inthis example embodiment, the message-3 transmission 655 is transmittedby the UE 610 at the required power to be ‘acceptably’ received at therelay device 615. This is due to the relay device 615 determining arequired power offset, in this example embodiment a power delta, of thetransmitted special group of RACH preambles 640.

In this example embodiment, the power delta relates to a differencebetween a desired maximum received power level of a transmission (suchas a RACH transmission) from the UE 610 and an actual received power ofthe transmission from the UE 610. The relay device 615 determines thispower offset from the received signal power of the transmitted specialgroup of RACH preambles 640, as described in more detail later.

The relay device 615 then relays in transmission 645 at least anindication of the determined power delta, along with the impliedinformation within the PRACH preamble. Thereafter, eNodeB 620 transmitsa random access response 650 to the UE 610 that includes the power deltadetermined by the relay device 615.

The UE 610 receives the random access response 650 and determinestherefrom the power delta requested by the intermediate relay device615. In response thereto, the UE 610 (may) alter its transmit powerbased on the received power delta indication, so that the subsequentmessage-3 transmission is transmitted at the (reduced) power level ofthe special group of RACH preambles, taking into account the powerdelta.

In this manner, the relay device 615 receives the subsequent message-3transmission at the required power level in order to be able to receiveand decode it correctly, without, for example, saturating the relaydevice's receiver. The relay device 615 is then able to relay themessage-3 to the eNodeB 620 in the desired manner.

In example embodiments, the special group of RACH preambles received atthe relay device 615 are relayed in 660 to the eNodeB 620 in a mediumaccess control (MAC) control element (as described, for example, withrespect to FIG. 8).

Also in this example at this moment in time, the relay device 615 maydetermine a further required/desired power offset, which may also berelayed to the eNodeB 620 in the MAC control element. The eNodeB 620 maytransmit a modified RAR (as described, for example, with respect to FIG.9), which may also contain the calculated power delta determined by therelay device 615.

FIG. 7 illustrates an example of an alternative simplified block diagram700 of a modified random access preamble transmission. In the previouslydescribed examples, it has been assumed that the UE continues to usemaximum transmission power when it switches from the maximum ramped uppower of, say the preamble transmission 735, to the power level to beused in transmitting the special group of RACH preambles 740. However,this process requires some form of closed loop control, wherein a powerdelta that identifies, for example, a difference between a desired powerlevel and an actual power level received at the relay device 715, has tobe relayed to the eNodeB 720 and subsequently transmitted to UE 710.However, in this illustrated example, once UE 710 has reached itsmaximum transmit power level for its group of RACH preambles 735, anddetermines that a special group of RACH preambles 740 needs to betransmitted, power ramping is employed with the special group of RACHpreambles, rather than transmitting the special group at maximum power.

As shown in FIG. 7, power ramping 740, 742 of the special group isemployed, until the relay device 715 successfully receives the specialgroup 744. The relay device 715 then relays the special group of RACHpreambles to eNodeB 720, which subsequently transmits a random accessresponse 750 to the UE 710. The UE 710 then uses the transmit power forthe successfully received preamble 744 when subsequently transmittingmessage-3 in communication 755, and possibly also with a systeminformation signalled offset (which is the conventional approach takenwhen no relay functionality is used). In this manner, it is possible todispense with a use of the power offset determined by the relay device,as described in previous embodiments, thereby producing an open loopsystem 700.

In another example embodiment, power offset information, as determinedby the relay device 715, is transmitted 745 with the successfully powerramped preamble information 744 to the eNodeB 720 as well as in theresponse 750 to the UE 710.

In some examples, the same power level may not be used, for example incases where a power level margin may be implemented for communicationsto/from UE 710. In this manner, a power level may be set that is not soclose to the minimum power level that supports successful reception anddecoding of communications to/from the UE 710.

In some example embodiments, the number of power ramping steps may bepre-determined, dynamically adjusted according to the prevailingoperational conditions or user defined, whereby the number of incrementsmay be set from one step to n steps and/or the power level range may beset accordingly.

In the case of the example embodiments of FIG. 6, and optionally FIG. 7,a new MAC control element and format may be required in order totransmit the power offset information to the eNodeB 710 via the relaydevice 715, an example of which is illustrated in, and described withrespect to, FIG. 8. Note that the new MAC control element may also beneeded for the example of FIG. 5, albeit that in this case the poweroffset information would not be needed.

As illustrated in FIG. 8, the relayed preamble message 800 may comprisea reserved part (R) 805, a timing advance part (TA command) 810, 815, arandom access preamble ID part (RAPID) 820, 825, a power offset (e.g.power control information) 830, a Random Access Temporary Identifier(RA-RNTI) 835 and optional padding (PAD) 840, which may be used to padthe message to the required size. A MAC header in the Random AccessResponse on the PDSCH may comprise one or more from a group of: a randomaccess preamble identifier that identifies the random access preamblereceived at eNodeB, a further temporary identifier (C-RNTI) foridentifying the terminal device, a grant of uplink resources on thePUSCH, and a timing advance command for adjusting transmission times atthe UE in dependence on the distance between the UE and the NodeB.

As well as a new MAC control element, a modified RAR may also be used,an example of which is illustrated in, and described with respect to,FIG. 9. A modified RAR message 900 is schematically illustrated in FIG.9. In particular, the modified RAR message 900 comprises a reserved part(R) 905, a timing advance part (TA command) 910, 915, an allocation ofuplink time and frequency resources (UL grant) 920, 925, 930, thefurther temporary identifier (C-RNTI) 935, 940, a power delta (Powercontrol information) 945 and optional padding (PAD) 950.

Calculating Power Offset

One example of a calculation of the aforementioned power offset is nowdescribed. The power offset, which in this example embodiment is a powerdelta, is based on a reception power level of the RACH transmission froma UE to a corresponding relay device. This value is then compared with apre-defined maximum receive power level that the relay device is able toreceive without saturating its receiver.

Currently, in the known art, a dedicated UE control element is containedin the 20-bit uplink (UL) grant information contained in a standard MACRAR. However, this control element is usually only three bits in lengthand provides, in general, a control range of −6 to +8 dB. In exampleembodiments of the invention, it is envisaged that this control elementmay be too small to deal with change in power, due in part to theabsence of path loss calculations. Thus, in some examples, a separatepower delta comprised in a separate part of the modified MAC RAR(illustrated with respect to FIG. 8, 9) may be used with a larger rangethan currently defined in the art.

In the known art, the UE determines the pathloss to the eNodeB andmodifies its preamble power based on this determination. In contrast,the relay device, in this example embodiment, is concerned with thereceive power of the relevant RACH preamble. As discussed above, aproblem may occur when a UE is unable to transmit a RACH preamble to acorresponding eNodeB, but is able to receive downlink information fromthe eNodeB. In this case, the UE generally transmits at full power,which, if relatively close to a relay device, can saturate the relaydevice's receiver. The relay device is unable to directly transmit tothe UE to inform it of the issue, due to an asynchronous system beingutilised in this example embodiment. Hence, in this example, the relaydevice is only/primarily interested in the receive power of thetransmission from the UE. In this embodiment, the pre-defined powerlevel that the relay device compares with the received power from the UEcan be any value. However, in this example embodiment, the pre-definedpower level is set at the expected power needed to decode the message 3transmission. In other embodiments, the pre-determined power level canbe dynamically changed during operation. In other embodiments, thepre-determined level may be fixed at some other value, such as a maximumpower that the relay device can receive a RACH transmission from the UE.

In the known art, for both PUSCH and PUCCH, a form of both closed andopen loop power control exists:

-   -   1. In the closed loop power control, the TPC commands are        successively transmitted back to the UE from the eNode B. In one        example, these are based on comparisons with a set        (pre-determined) level that the eNodeB expects to receive from        the UE. For example the previously mentioned 3-bit δ_(msg2)        parameter used to control power in range −6 to +8 dB may be used        as a form of TPC command (informing the UE to increase or        decrease its TX power by, say, a relatively small amount).        Typically, TPC commands would be accumulated.    -   2. The open loop power control for PUSCH/PUCCH may employ        nominal target level reception parameters signalled by the node        B, for example offsets based on the grant received (the        modulation and coding scheme or the number of subcarriers) and        notably the pathloss to the eNodeB.

One problem with such a known relay device-assisted architecture is thatthe pathloss from the UE to the RN cannot be measured or used. Thus,examples of the invention may remove the pathloss component and thenominal target level parameters from the set of open loop parameters andreplace them with a direct definition of the power used for a message 3transmission. In some examples, the TPC commands then act to change thepower of the PUSCH as required.

FIG. 10 illustrates a simplified message sequence chart 1000 of amodified random access preamble transmission, according to an exampleembodiment of the invention. The operation of FIG. 10, surrounded by thedashed box 1001, is similar to that described in previous exampleembodiments, specifically the example embodiment relating to FIG. 6.Therefore, only new features will be discussed hereafter. It should benoted that the operation of the example embodiment relating to FIG. 10is not limited to the preceding messages described with reference toFIG. 6, and may equally be used with other example embodiments,singularly or in combination with other aspects of the invention.

Thus, FIG. 10 further illustrates subsequent communications between UE1015, relay device 1020, and eNodeB 1025. In this example, thesubsequent communications may comprise transmissions on a PhysicalUplink Shared CHannel (PUSCH) 1005 and/or a Physical Uplink ControlCHannel (PUCCH) 1010. In this example embodiment, both PUSCH and PUCCHsignals are transmitted from the UE 1015 to the relay device 1020.

As discussed above, a problem may arise in scenarios when UE 1015transmits at maximum power, as a receiver of the relay device 1020, iflocated close to the UE 1015, may saturate, as known in the art. Torecap, in some example embodiments and as illustrated in FIG. 10, relaydevice 1020 determines a power offset from the received signal power ofa transmitted special group of RACH preambles 640. The relay device 1020is then operable to relay 645 the determined power delta with thespecial group of RACH preambles 640 to eNodeB 620. ENodeB 620 is thenoperable to transmit a random access response 650 that includes thepower delta determined by the relay device 1020. The UE 1015 receivesthe random access response 650 and power delta, and alters itstransmission power in response to the received power delta so that thesubsequent message-3 transmission is transmitted at the power of thespecial group of RACH preambles including the power delta.

Therefore the relay device 1020 receives the message-3 transmission atthe required power to be able to receive it correctly, withoutsaturating the relay device's receiver.

In this example embodiment, subsequent PUSCH 1005 and PUCCH 1010transmissions utilise the power delta relayed in 650, thereby ensuringthat subsequent transmissions will be received and may be correctlydecoded by the relay device 1020. In this example embodiment, thetransmission power of PUSCH 1005 and PUCCH 1010 is only based on theinitial power of the message-3 transmission 655. In other exampleembodiments, the PUSCH 1005 and PUCCH 1010 transmission power may befurther based on the contents of the MAC RAR message, as discussedabove, rather than the power needed to obtain a successful RACHresponse.

Further example embodiments may base the power level of PUSCH 1005 andPUCCH 1010 transmissions based on a transmit power control (TPC)modification of the message-3 transmission 655 and/or open loopparameters based on the grant.

Further, in the PUCCH transmission 1010 case, other embodiments mayadditionally base the transmission power level on open loop common deltaparameters based on the PUCCH 1010 format and the number of bits used toencode CQI/HARQ.

In essence, the PUCCH case is similar to that of the PUSCH case, in thatthe pathloss to the RN cannot be measured, and hence the use of apathloss value plus a nominal received level at the eNodeB cannot beused. Thus, the power used for message 3 transmission plus accumulatedTPC commands are relied upon, without any open loop pathlossdetermination or distribution.

Transmission of PUSCH and PUCCH

In order for UE 1015 to be able to set the transmission power of PUSCH1005 and PUCCH 1010 accurately, based on at least message-3 transmissionpower, the behaviour of the UE 1015 needs to be modified from that knownin the art.

In the below example, referring to a standard measurement defined in theart, setting the UE 1015 transmission power, P_(PUSCH), for the physicaluplink shared channel 1005 transmission in a subframe ‘i’ is definedby:—

P _(PUSCH)(i)=min{P _(CMAX),10 log₁₀(M _(PUSCH)(i))+P _(O) _(—)_(PUSCH)(j)+α(j)·PL+Δ _(TF)(i)+f(i)} [dBm]

In this example:

-   -   P_(CMAX) is the configured UE transmitted power defined in 3GPP        TS 36.101 and is basically the maximum power that the UE is        allowed to transmit at—based on its power class.    -   M_(PUSCH)(i) is the bandwidth of the PUSCH resource assignment        expressed by the number of resource blocks valid for a subframe        ‘i’.    -   P_(O) _(—) _(PUSCH)(j) is a parameter composed of the sum of a        cell specific nominal component P_(O) _(—) _(NOMINAL) _(—)        _(PUSCH)(j) provided from higher layers for j=0 and 1, and a UE        specific component P_(O) _(—) _(UE) _(—) _(PUSCH)(j) provided by        higher layers for j=0 and 1.    -   α(j) is a parameter between ‘0’ and ‘1’ defined by higher        layers. It is used as part of the fractional power control        functionality. Typically, it would be set to ‘1’ so that the        pathloss is fully compensated and the fractional power control        functionality is disabled.    -   PL is the path loss from the UE to the eNodeB;    -   Δ_(TF) is an offset function based on the MCS indicated in the        grant in the associated PDCCH.    -   f(i) is the closed loop element of the power control function.        It is based on the TPC commands that are received back from the        eNode B in downlink control information (formats 0 and 3/3A)        included in the PDCCH (note that, as has been discussed above,        there is also a TPC command element in the UL grant in the RAR        also). TPC commands can either be accumulated or not (this        option is configured using RRC signalling).

If accumulation is employed then: f(i) represents the accumulated TPC inthe i^(th) subframe and thus the value of f(i) is:f(i)=f(i−1)+δPUSCH(i−4). Where −PUSCH(i−4) is the TPC command received 4frames ago. Note that this is 4 subframes ago due to the operation ofthe UL HARQ cycle in FDD.

If accumulation is not employed then f(i) is simply the absolute valueof the last associated TPC command, due to the HARQ cycle in FDD this is4 frames ago. Thus f(i)=δPUSCH(i−4).

For both types of f(*) (accumulation or current absolute) the firstvalue is set as follows:

If P_(O) _(—) _(UE) _(—) _(PUSCH) value is changed by higher layers,

f(0)=0

Else

f(0)=ΔP_(rampup)+δ_(msg2)

where δ_(msg2) is the TPC command indicated in the random accessresponse, see 3GPP TS 36.213 section 6.2 that describes how thepreviously mentioned 3-bit parameter is mapped to the range −6 dB to +8dB, and

ΔP_(rampup) is provided by higher layers and corresponds to the totalpower ramp-up from the first to the last preamble.

In some example embodiments, PUSCH (re)transmissions may correspond to asemi-persistent grant, j=0.

In other example embodiments, PUSCH (re)transmissions may correspond toa dynamic scheduled grant, j=1.

In further example embodiments, PUSCH (re)transmissions may correspondto a random access response, j=2, for example:

-   -   P_(O) _(—) _(UE) _(—) _(PUSCH)(2)=0 and P_(O) _(—) _(NOMINAL)        _(—) _(PUSCH)(2)=P_(O) _(—) _(PRE)+Δ_(PREAMBLE) _(—) _(Msg3),        where the parameter PREAMBLE_INITIAL_RECEIVED_TARGET_POWER [8]        (P_(O) _(—) _(PRE)) and Δ_(PREAMBLE) _(—) _(msg3) are signalled        from higher layers. For j=0 or 1, αε{0, 0.4, 0.5, 0.6, 0.7, 0.8,        0.9, 1} is a 3-bit cell specific parameter provided by higher        layers. For j=2, α(j)=1.

In the example embodiment of FIG. 10, the above known equation has beenamended based on aspects of the claimed invention. UE 1015, using relaydevice 1020 as an intermediary communication network element, determinesa PUSCH transmission power level for a message-3 transmission as:—

Ppusch=min(P _(cmax),transmission power of success preamble in max powergroup+10 log 10(MPUSCH(i))+ΔTF(i)+delta defined in MAC RAR).

Where the delta defined in the MAC RAR is the (modified RAR MAC controlelement) power delta parameter 945 in FIG. 9.

In other example embodiments, UE 1015 using relay device 1020 determinesPUSCH transmission power levels for non message-3 cases as:—

Ppusch(i)=min(P _(CMAX),message 3 TX power+10 log10(MPUSCH(i))+ΔTF(i)+f(i)

By utilising the above amended equations, it is possible to determine atransmit value for PUSCH based on a message-3 transmission. In this way,it can be assured that the subsequent PUSCH transmission can be receivedby the relay device 1020 without saturation of the relay device'sreceiver. Further, subsequent PUSCH transmissions are determined withouta need for a path loss component.

In this example embodiment, in order to determine the correct PUCCHtransmission power, the UE 1005 utilises the determined message-3transmission power and baselines (sets the reference to) all futurePUCCH transmissions to this message-3 transmission power.

In another example embodiment, all future PUCCH transmissions may bedynamically configured based, in part, on message-3 transmission power.

In the below example, referring to a standard measurement defined in theart, setting the UE 1015 transmission power, P_(PUCCH) for the physicaluplink control channel 1010 transmission in a subframe ‘i’ is definedby:—

P _(PUCCH)(i)=min{P _(CMAX) ,P ₀ _(—) _(PUCCH) PL+h(n _(CQI) ,n_(HARQ))+Δ_(F) _(—) _(PUCCH)(F)+g(i)} [dBm]

In this example embodiment, P_(CMAX) is the configured UE transmittedpower defined in 3GPP TS 36.101, where:

-   -   PL is the UE measured path loss;    -   g(i) is the closed loop element of the power control function        for PUCCH. It is similar to the case for PUSCH described above.        The parameter is based on TPC commands received from the eNode B        in downlink control information (formats 1A/1B/1D/1, 2A/2B/2 and        3/3A). Accumulation of TPC commands is mandatory for the PUCCH        case. Thus, in the i^(th) subframe g(i)=g(i−1)+δPUCCH(i−4).        Where δPUCCH(i−4) is the TPC command received in the PDCCH 4        subframes ago. As for the PUSCH case the 4 frames are required        to deal with the operation of the HARQ cycle.    -   The parameters Δ_(F) _(—) _(PUCCH)(F) and h(n_(CQI),n_(HARQ))        are offset parameters based on the PUCCH format that is being        used.

P_(O) _(—) _(PUCCH) is a parameter composed of the sum of a cellspecific parameter P_(O) _(—) _(NOMINAL) _(—) _(PUCCH) provided byhigher layers and a UE specific component P_(O) _(—) _(UE) _(—) _(PUCCH)provided by higher layers.

In the example embodiment of FIG. 10, the above known equation has beenamended based on features of the claimed invention. UE 1015 using relaydevice 1020 determines PUCCH transmission power for message 3 as:—

Ppusch(i)=min(P _(CMAX),message 3 TX power+h(n _(CQI) ,n _(HARQ))+Δ_(F)_(—) _(PUCCH)(F)+g(i)

In another example embodiment, the transmission power of PUCSH 1005 andPUCCH 1010 may be based on the value of message-3 transmissionsdetermined using power ramping, as discussed in FIG. 7, therebyproducing open loop control of the PUCSH 1005 and PUCCH 1010 signals.

In some example embodiments, the TPC command δ_(msg2) may be used fordetermining a power level for the special case of the PUSCH used to senda message 3 transmission (i.e. the first PUSCH transmission that the UEmakes after a random access procedure), noting that a different TPCcommand structure is used for all other cases. The TPC command for aPUSCH used to send a message 3 transmission may be interpreted, say,according to the values in Table 1.

TABLE 1 TPC Command δ_(msg 2) for scheduled PUSCH TPC Command Value (indB) 0 −6 1 −4 2 −2 3 0 4 2 5 4 6 6 7 8

Referring back to FIG. 9, it is recognized that the performance rangeprovided by known systems is not large enough to accommodate a new powerdelta control element. Therefore, as illustrated with respect to FIG. 9,a new MAC power delta control element 945 may be introduced as anadditional field in the MAC RAR 900. In this example, the MAC powerdelta control element 945 may be used instead of δ_(msg2).

However, in some instances, the use of a MAC power delta control element945 may require the structure of the MAC RAR 900 in FIG. 9 to be octetaligned. The addition of a power delta control element 945, therebyresults in an additional field of at least 8 bits, for example usingoptional padding (PAD) bits 950.

In some examples, the power delta control element 945 may be used tocontrol UE power with a granularity of 0.5 dB. In this case, powercontrol of the UE could be effected over 128 dB (noting that an 8-bitfield provides 256 values). However, in most telecommunicationsimplementations, a typical range comprising 60 to 80 dB is employed.Therefore, in this example, some resource may be wasted, as more datacould be transmitted than is actually used.

In some examples, therefore, the abovementioned MAC RAR 900, withadditional power delta control element 945, may be deemed inefficient.In order to address this potential problem in some instances, theinventors have recognized that, in this example, the timing advancefield 910, 915 may be too large for current uplink relaying scenarios.The typical timing advance field is an 11-bit timing advance field thatallows timing of ‘0’ to ‘20512’ symbol periods. However, not all of the11 bits are utilised. Generally, values from ‘0’ to ‘1282’ are signaledand each value may have a granularity of 16 symbol periods, whichequates to 16*1282=20512 symbol periods. In LTE, this provides a timingadvance of around 0.67 msec., which, in some examples, may support acommunication cell radius of around 100 km (taking into consideration around trip), which is excessive for most practical synchronous relaysystem scenarios. In an asynchronous (uplink only) relay systemscenario, where relay nodes are located generally closer to the basestations, such granularity of the timing advance may be consideredwasteful. Thus, in some examples, the timing advance part, in FIG. 9illustrated as 910, 915, which typically comprise 11 bits, may providesome unused bits that are used to create a smaller power delta field.

In one example embodiment, the timing advance field may be reduced to 7bits, thereby allowing signaling of ‘0’ to ‘127’ values, or ‘0’ to‘127’*16 (i.e. 2032) symbol periods. In this example, this may result ina maximum timing advance of 4 μs that is equivalent to a cell radius ofaround 600 m (taking into consideration a round trip). In most practicalscenarios, this may be deemed sufficient for an uplink only relayingscenario. Therefore, in this example embodiment, the power delta fieldmay be used instead of: δ_(msg2).

FIG. 11 illustrates an example of a prior art MAC RAR 1100, as generallydefined in the art, shown in conjunction with a modified MAC RAR 1150,as per the abovementioned example. MAC RAR 1100 comprises a reservedpart (field) 1105, a timing advance part 1110, 1115, which in thisexample comprises 11 bits, an uplink grant part 1120, 1125, 1130, whichin this example comprises 20 bits, and a temporary C-RNTI part 1135,1140, which in this example comprises 16 bits. The hatched regionillustrates the timing advance part 1110, 1115.

Modified MAC RAR 1150 according to example embodiments of the inventioncomprises a number of similar elements/parts to known MAC RAR 1100.However, a primary difference provided by modified MAC RAR 1150, in thisexample, is in the shaded regions 1160 and 1165. In this example, timingadvance part 1160 has been reduced to 7 bits, and a power delta part1165 has been incorporated into (replacing) 4 bits of the prior arttiming advance 1115. In other examples, the reserved part (field) 1105may be used as part of the timing advance field, in order to make thetiming advance up to 8 bits.

In examples, the UE and eNodeB may know when to utilise the modified MACRAR 1150, due, in part, because the max power PRACH preamble group mayhave been utilised.

An example of utilising the power delta (4 bits) 1165 could be performedas illustrated in Table. 2 below. It should be noted that Table. 2should not be seen as an exact interpretation of the 4 bits that may bespecified for the power delta, and any alternative reasonable orperceived approach may be used, so long as in some instances relativelylarge negative offsets may be supported.

In this example, the power delta field 1165 replaces δ_(msg2).

TABLE 2 Power delta with simple 4 bit field Value of power offset fieldin Power offset RAR (dB) 0 −70 1 −65 2 −60 3 −55 4 −50 5 −45 6 −40 7 −358 −30 9 −25 10 −20 11 −15 12 −10 13 −5 14 0 15 5 16 10

In this example, even with a 4-bit power delta field, the granularity isof the order of 5 dB.

In other examples, it may be desirable to reduce the granularity in theabovementioned example. In some examples, it may be advantageous toutilise the information in δ_(msg2), and incorporate this with theinformation within the new power delta field 1165. This may allow thegranularity to be reduced, without affecting the number of bits of thepower delta 1165.

FIG. 12 illustrates a further modified MAC RAR 1200 according to someexamples of the invention. In this example, MAC RAR 1200 essentiallycomprises the same parts as MAC RAR 1100. A main difference being thatthe timing advance part 1210, 1215 may now comprise 8 bits. Further, thepower delta part 1218 may comprise 3 bits. Again, in other examples, thereserved part (field) 1105 may be used as part of the timing advancefield, in order to make the timing advance up to a 9-bit field

In some examples, the range of δ_(msg2) is generally 14 dB (+8 dB to −6dB, for example). If the new power delta 1218 comprised a step of 15 dB,as illustrated in Table 3, then it would be possible to use δ_(msg2) inaddition to the new power delta 1218, in order to fill in between steps,for example where the new power delta 1218 provides a quick step to theadditional finer granularity provided by δ_(msg2).

TABLE 3 Example of a bit implementation when power delta is used inconjunction with δ_(msg 2). Value of power offset field in Power offsetRAR (dB) 0 −105 1 −90 2 −75 3 −60 4 −45 5 −30 6 −15 7 0

Table 3 illustrates an example of an implementation when new power delta1218 is used in conjunction with δ_(msg2). For example, if a UE were tobe instructed to reduce its power by 52 dB, the new power delta field1218 may signal, say, −60 dB, and the δ_(msg2) may signal +8 dB, thecombined effect being −52 dB. Therefore, in this example, only a 3-bitpower delta 1218 is required. In the above example, an offset of +8 dBto −111 dB is possible, with a granularity of approximately 2 dB.

This may be interpreted in the same manner as currently specified in3GPP TS36.213. Further, in this example, as only 3 bits may be used forthe power delta 1218, an extra bit is available for use by the timingadvance part 1210.

In one example, timing advance part 1210 may comprise 8 bits. In anotherexample, timing advance part may comprise 9 bits, if, for example, thereserved part 1105 is utilised.

In this example, a timing advance part 1210 comprising, for example, 8bits, may double the timing advance range, compared to FIG. 11. In thisexample, the maximum cell radius may be around 1.2 km, which is wellabove what is anticipated for the uplink only relaying case. In someexamples, the number of timing advance bits being stolen may bedetermined as a function of the cell radius required to support usefulcommunications with UEs, thereby avoiding any inefficiency/wastage ofstolen timing advance bits.

In further examples, it may be advantageous to maintain the current MACRAR 1100, as defined in the art, but alter a UE's interpretation ofδ_(msg2) if it has sent its PRACH (special set) preamble using the maxpower group, for example. An example of a possible modification to theδ_(msg2) mapping is illustrated in table 4.

TABLE 4 TPC command δ_(msg 2) for scheduled PUSCH when UE has used a newPRACH max preamble group. TPC Command Value (in dB) 0 −50 1 −40 2 −30 3−20 4 −10 5 0 6 5 7 10

Thus, as shown in some examples, it is possible to maintain the generalformat of the known MAC RAR 1100, whilst additionally providing variousconfigurations of power control to a UE in a relay-assisted uplinkscenario.

FIG. 13 illustrates an example flow chart 1300 employed by a terminaldevice encompassing aspects of the invention. At 1302, the terminaldevice is operable to transmit RACH preambles to at least one eNodeB. At1304, the terminal device determines whether a corresponding RACHresponse has been transmitted from at least one eNodeB. If the terminaldevice determines that a corresponding RACH response has beentransmitted from at least one eNodeB in 1304, the terminal devicetransmits a message 3 transmission at 1308. If the terminal devicedetermines that a corresponding RACH response has not been transmittedfrom at least on eNodeB in 1304, the terminal device determines, at1306, whether it has reached its maximum transmit power. If the terminaldevice determines that it has not reached its maximum transmit power in1306, the terminal device ramps up its transmitter power at 1310 andreturns to 1302. If the terminal device determines that it has reachedits maximum transmit power in 1306, the terminal device may transmit a‘special group of RACH preambles’ to the at least one eNodeB via a relaydevice at 1312, as described previously.

The terminal device may then receive a corresponding modified RAR fromthe at least one eNodeB with a power delta value, at 1314. In responseto this received modified RAR, the terminal device may transmit amessage 3 to the corresponding at least one eNodeB based on at least thevalue of the received power delta in 1320, as instructed by the at leastone eNodeB. In some examples, the at least one eNodeB may (or may not)include one or more of the aforementioned options of mapping theδ_(msg2) power range in 1316 or a stealing timing advance bits of 1318.As the terminal device (UE) knows that its communication us beingrelayed, following transmission of the special set of preambles and areceipt of a corresponding modified RAR in response thereto, theterminal device (UE) knows the format of the modified RAR and, thus,knows how to decode it correctly to determine the instructions.

For example, the terminal device may, as instructed by the at least oneeNodeB, utilise mapping at 1316 to modify the power range of δ_(msg2),where the mapping may be utilised in response to the terminal devicerecognizing that a relay device is being used in the communication byreceiving a response to the ‘special group of RACH preambles. In thisexample, the at least one eNodeB may also recognize that a relay deviceis being used in the communication by receiving the ‘special group ofRACH preambles and in one example be notified of the terminal device'sintention to utilise a modified power range of δ_(msg2). The terminaldevice may then proceed to transmit message 3 to the at least one eNodeBbased on at least the value of the received power delta.

In another example, the eNodeB may also inform/instruct the terminaldevice to recover/decode the, received power delta value from replacedtiming advance bits in the message 3 transmission (with or withoutinitializing the mapping option of 1316). Advantageously, the stealingof timing advance bits without having to introduce a new layer to themessage 3 protocol stack, increases an efficiency of the transmittedprotocol stack. In a further example, the terminal device may utiliseboth of 1316 and 1318 before transmitting in 1320 a message-3 to thebase station (eNodeB) based on at least the value of the received powerdelta.

Referring now to FIG. 14, there is illustrated a flow chart 1400 of anoperation of a relay device encompassing aspects of the invention. At1402, the relay device is operable to receive RACH preambles transmittedfrom at least one UE. If the relay device determines, at 1406, that thereceived RACH preambles are a ‘special group of RACH preambles’, therelay device continues to 1408; otherwise the relay device returns to1402.

At 1408, the relay device may determine a power delta based on, atleast, the received power of the transmitted ‘special group of RACHpreambles’. In an example embodiment, the received power of thetransmitted ‘special group of RACH preambles’ may be further comparedwith a desired power level. At 1410, the relay device relays, at least,an indication of the determined power delta together with the impliedinformation associated with a reception of the ‘special group of RACHpreambles’ (RAPID, RA-RNTI and timing advance command, as illustrated inFIG. 8) to the eNodeB. At this point, the eNodeB may be operable totransmit a random access response that may include the power deltadetermined by the relay device. At 1412, the relay device is operable toreceive a subsequent message-3 transmission from the UE at the requiredpower level to enable the relay device to receive and decode themessage-3 transmission correctly without saturating the relay device'sreceiver. At 1414, the relay device is operable to relay the message-3transmission to the eNodeB and the process ends.

FIG. 15 illustrates a flow chart of an operation of a base stationencompassing aspects of the invention. At 1502, the base stationreceives access attempts from at least one terminal device. At 1504, thebase station determines whether (or not) the received RACH preambles areconventional RACH preambles or via a relayed MAC control element. If thereceived RACH preambles are conventional RACH preambles, in which casethe base station measures the received power and determines a requiredpower delta at 1506 and measures a timing of the UE transmission anddetermines a required timing advance at 1508. The base station thenconstructs a conventional RAR at 1510 and transmits the conventional RARat 1512 to the corresponding at least one terminal device. Note that thebase station (eNodeB) doesn't need the large power deltas needed for therelay case as the UE has been able to work out a pathloss to the basestation (eNodeB) and power control itself appropriately, due to thebeacon.

If the base station (eNodeB) determines that the access attempt was viathe special group of RACH preambles comprising a relayed MAC controlelement, in 1504, i.e. indicative of a relay device uplink, the basestation (eNodeB) extracts the required delta and timing advance in 1514.The base station (eNodeB) then constructs a modified RAR in 1516 andtransmits the modified RAR to the corresponding at least one terminaldevice (UE) with a corresponding power delta calculated by at least onerelay device, at step 1518.

Referring now to FIG. 16, there is illustrated a typical computingsystem 1600 that may be employed to implement software-controlled powercontrol functionality in embodiments of the invention that utilize anintermediary relay device between a terminal device, such as a UE, and abase station, such as an eNodeB. Computing systems of this type may beused in wireless communication units, such as first or second wirelessnetwork elements. Those skilled in the relevant art will also recognizehow to implement the invention using other computer systems orarchitectures. Computing system 1600 may represent, for example, adesktop, laptop or notebook computer, hand-held computing device (PDA,cell phone, palmtop, etc.), mainframe, server, client, or any other typeof special or general purpose computing device as may be desirable orappropriate for a given application or environment. Computing system1600 can include one or more processors, such as a processor 1604.Processor 1604 can be implemented using a general or special-purposeprocessing engine such as, for example, a microprocessor,microcontroller or other control logic. In this example, processor 1604is connected to a bus 1602 or other communications medium.

Computing system 1600 can also include a main memory 1608, such asrandom access memory (RAM) or other dynamic memory, for storinginformation and instructions to be executed by processor 1604. Mainmemory 1608 also may be used for storing temporary variables or otherintermediate information during execution of instructions to be executedby processor 1604. Computing system 1600 may likewise include a readonly memory (ROM) or other static storage device coupled to bus 1602 forstoring static information and instructions for processor 1604.

The computing system 1600 may also include information storage system1610, which may include, for example, a media drive 1612 and a removablestorage interface 1620. The media drive 1612 may include a drive orother mechanism to support fixed or removable storage media, such as ahard disk drive, a floppy disk drive, a magnetic tape drive, an opticaldisk drive, a compact disc (CD) or digital video drive (DVD) read orwrite drive (R or RW), or other removable or fixed media drive. Storagemedia 1618 may include, for example, a hard disk, floppy disk, magnetictape, optical disk, CD or DVD, or other fixed or removable medium thatis read by and written to by media drive 1612. As these examplesillustrate, the storage media 1618 may include a computer-readablestorage medium having particular computer software or data storedtherein.

In alternative embodiments, information storage system 1610 may includeother similar components for allowing computer programs or otherinstructions or data to be loaded into computing system 1600. Suchcomponents may include, for example, a removable storage unit 1622 andan interface 1620, such as a program cartridge and cartridge interface,a removable memory (for example, a flash memory or other removablememory module) and memory slot, and other removable storage units 1622and interfaces 1620 that allow software and data to be transferred fromthe removable storage unit 1618 to computing system 1600.

Computing system 1600 can also include a communications interface 1624.Communications interface 1624 can be used to allow software and data tobe transferred between computing system 1600 and external devices.Examples of communications interface 1624 can include a modem, a networkinterface (such as an Ethernet or other NIC card), a communications port(such as for example, a universal serial bus (USB) port), a PCMCIA slotand card, etc. Software and data transferred via communicationsinterface 1624 are in the form of signals which can be electronic,electromagnetic, and optical or other signals capable of being receivedby communications interface 1624. These signals are provided tocommunications interface 1624 via a channel 1628. This channel 1628 maycarry signals and may be implemented using a wireless medium, wire orcable, fiber optics, or other communications medium. Some examples of achannel include a phone line, a cellular phone link, an RF link, anetwork interface, a local or wide area network, and othercommunications channels.

In this document, the terms ‘computer program product’,‘computer-readable medium’ and the like may be used generally to referto media such as, for example, memory 1608, storage device 1618, orstorage unit 1622. These and other forms of computer-readable media maystore one or more instructions for use by processor 1604, to cause theprocessor to perform specified operations. Such instructions, generallyreferred to as ‘computer program code’ (which may be grouped in the formof computer programs or other groupings), when executed, enable thecomputing system 1600 to perform functions of embodiments of the presentinvention. Note that the code may directly cause the processor toperform specified operations, be compiled to do so, and/or be combinedwith other software, hardware, and/or firmware elements (e.g., librariesfor performing standard functions) to do so.

In an embodiment where the elements are implemented using software, thesoftware may be stored in a computer-readable medium and loaded intocomputing system 1600 using, for example, removable storage drive 1622,drive 1612 or communications interface 1624. The control logic (in thisexample, software instructions or computer program code), when executedby the processor 1604, causes the processor 1604 to perform thefunctions of the invention as described herein.

In one example, a tangible non-transitory computer program productcomprises executable program code operable for, when executed at aterminal device arranged to communicate with a base station via a relaydevice in a wireless communications system, performing the steps of:transmitting an access request message, wherein the access requestmessage comprises one from a set of access preambles that indicate relaydevice uplink assistance is required; receiving an access request grantresponse from the base station; processing the access request grantresponse and determine from a timing advance part thereof transmit powercontrol (TPC) information for transmitting to the base station via therelay device.

In one example, a tangible non-transitory computer program productcomprises executable program code operable for, when executed at a basestation arranged to communicate with a terminal device via a relaydevice in a wireless communications system, performing the steps of:receiving an access request message from the terminal device; processingthe access request message and extract a relayed control element thatindicates relay device uplink assistance was used wherein the relayedcontrol element comprises a power delta from the relay device;constructing an access request grant response message wherein the accessrequest grant response comprises a larger field for power control and acomparable smaller field for timing advance information for use inrelayed communications as compared to corresponding size of fields foruse in non-relayed communications; and transmitting the access requestgrant response to the terminal device.

It will be appreciated that, for clarity purposes, the above descriptionhas described embodiments of the invention with reference to differentfunctional units and processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits or processors, without detracting from the invention. For example,functionality illustrated to be performed by separate processors orcontrollers may be performed by the same processor or controller. Hence,references to specific functional units are only to be seen asreferences to suitable means for providing the described functionality,rather than indicative of a strict logical or physical structure ororganization.

Aspects of the invention may be implemented in any suitable formincluding hardware, software, firmware or any combination of these. Theinvention may optionally be implemented, at least partly, as computersoftware running on one or more data processors and/or digital signalprocessors. Thus, the elements and components of an embodiment of theinvention may be physically, functionally and logically implemented inany suitable way. Indeed, the functionality may be implemented in asingle unit, in a plurality of units or as part of other functionalunits.

Those skilled in the art will recognize that the functional blocksand/or logic elements herein described may be implemented in anintegrated circuit for incorporation into one or more of thecommunication units. One example of the integrated circuit that issuitable for a network element, such as a relay device for providingintermediary communications between a wireless communication unit and aneNodeB, is the relay device control processor.

One example of an integrated circuit for a terminal device is arrangedto communicate with a base station via a relay device in a wirelesscommunications system. The integrated circuit comprises: a controlprocessor arranged to: transmit an access request message wherein theaccess request message comprises one from a set of access preambles thatindicate relay device uplink assistance is required; receive an accessrequest grant response from the base station; process the access requestgrant response; and determine from a timing advance part thereoftransmit power control (TPC) information for transmitting to the basestation via the relay device.

One example of a further integrated circuit that is suitable for a basestation arranged to communicate with a terminal device on an uplinkchannel via a relay device in a wireless communications system, wherethe integrated circuit comprises a control processor arranged to:receive an access request message from the terminal device; process theaccess request message and extract a relayed control element thatindicates relay device uplink assistance was used wherein the relayedcontrol element comprises a power delta from the relay device; constructan access request grant response message wherein the access requestgrant response comprises a larger field for power control and acomparable smaller field for timing advance information for use inrelayed communications as compared to corresponding size of fields foruse in non-relayed communications; and transmit the access request grantresponse to the terminal device.

Furthermore, it is intended that boundaries between logic blocks aremerely illustrative and that alternative embodiments may merge logicblocks or circuit elements or impose an alternate composition offunctionality upon various logic blocks or circuit elements. It isfurther intended that the architectures depicted herein are merelyexemplary, and that in fact many other architectures can be implementedthat achieve the same functionality. For example, for clarity, thesignal processing module of the first network element has beenillustrated and described as a single processing module, whereas inother implementations it may comprise separate processing modules orlogic blocks.

Although the present invention has been described in connection withsome example embodiments, it is not intended to be limited to thespecific form set forth herein. Rather, the scope of the presentinvention is limited only by the accompanying claims. Additionally,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognize thatvarious features of the described embodiments may be combined inaccordance with the invention. In the claims, the term ‘comprising’ doesnot exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by, for example, a singleunit or processor. Additionally, although individual features may beincluded in different claims, these may possibly be advantageouslycombined, and the inclusion in different claims does not imply that acombination of features is not feasible and/or advantageous. Also, theinclusion of a feature in one category of claims does not imply alimitation to this category, but rather indicates that the feature isequally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply anyspecific order in which the features must be performed and in particularthe order of individual steps in a method claim does not imply that thesteps must be performed in this order. Rather, the steps may beperformed in any suitable order. In addition, singular references do notexclude a plurality. Thus, references to ‘a’, ‘an’, ‘first’, ‘second’,etc. do not preclude a plurality.

1. A terminal device arranged to communicate with a base station via arelay device in a wireless communications system, the terminal devicecomprising: a transmitter arranged to transmit an access request messagewherein the access request message comprises one from a set of accesspreambles that indicate relay device uplink assistance is required; areceiver arranged to receive an access request grant response from thebase station; and a control processor operably coupled to thetransmitter and receiver and arranged to: process the access requestgrant response and determine from a timing advance part thereof transmitpower control (TPC) information for transmitting to the base station viathe relay device.
 2. The terminal device of claim 1 wherein thetransmitter is arranged to first transmit an access request message tothe base station a number of times at an increasing power level; andtransmit, upon failure to receive a response to said access requestmessages, the access request message that comprises one from a set ofaccess preambles that indicate relay device uplink assistance isrequired to the base station.
 3. The terminal device of claim 1 whereinthe access request grant response comprises at least one from a groupof: a reserved part, a timing advance part, a random access preambleidentifier part, an allocation of uplink resources, a power delta, atleast one temporary Identifier, padding.
 4. The terminal device of claim1 wherein the control processor determines from the access request grantresponse a number of timing advance bits that have been replaced withthe TPC information.
 5. The terminal device of claim 4 wherein a numberof timing advance bits being replaced is determined as a function of anaccuracy of a power delta for power control of the terminal device. 6.The terminal device of claim 4 wherein a number of timing advance bitsbeing replaced is determined as a function of a cell radius of a servingbase station.
 7. The terminal device of claim 1 wherein the controlprocessor determines a δ_(msg2) TPC command from the power controlinformation.
 8. The terminal device of claim 7 wherein the transmittertransmits a subsequent message on a physical uplink shared channel(PUSCH) to the relay device at a power level that is based on theδ_(msg2) TPC command.
 9. The terminal device of claim 7 wherein theδ_(msg2) TPC command is not based on a determination of pathloss betweenthe relay device and the terminal device.
 10. An integrated circuit fora terminal device arranged to communicate with a base station via arelay device in a wireless communications system, the integrated circuitcomprising: a control processor arranged to: transmit an access requestmessage, wherein the access request message comprises one from a set ofaccess preambles that indicate relay device uplink assistance isrequired; receive an access request grant response from the basestation; process the access request grant response and determine from atiming advance part thereof transmit power control (TPC) information fortransmitting to the base station via the relay device.
 11. A method fora terminal device arranged to communicate with a base station via arelay device in a wireless communications system, the method comprising:transmitting an access request message, wherein the access requestmessage comprises one from a set of access preambles that indicate relaydevice uplink assistance is required; receiving an access request grantresponse from the base station; processing the access request grantresponse and determine from a timing advance part thereof transmit powercontrol (TPC) information for transmitting to the base station via therelay device.
 12. A non-transitory computer program product comprisingexecutable program code to wirelessly communicate data from a terminaldevice to a base station via a relay device, the executable program codeoperable for, when executed at the terminal device, performing themethod of claim
 11. 13. A wireless communication system comprising: atleast one terminal device; at least one base station; and at least onerelay device for supporting communications between the at least oneterminal device and the at least one base station, wherein the at leastone terminal device comprises: a transmitter arranged to transmit anaccess request message, wherein the access request message comprises onefrom a set of access preambles that indicate relay device uplinkassistance is required; a receiver arranged to receive an access requestgrant response from the base station; and a control processor operablycoupled to the transmitter and receiver and arranged to: process theaccess request grant response and determine from a timing advance partthereof transmit power control (TPC) information for transmitting to thebase station via the relay device.
 14. A base station arranged tocommunicate with a terminal device on an uplink channel via a relaydevice in a wireless communications system, the base station comprising:a receiver arranged to receive an access request message from theterminal device; and a control processor operably coupled to thereceiver and arranged to: process the access request message; extract arelayed control element that indicates relay device uplink assistancewas used wherein the relayed control element comprises a power deltafrom the relay device; and construct an access request grant responsemessage wherein the access request grant response comprises a largerfield for power control and a comparable smaller field for timingadvance information for use in relayed communications as compared tocorresponding size of fields for use in non-relayed communications; andtransmit the access request grant response to the terminal device. 15.The base station of claim 14 wherein the control processor determines anumber of timing advance bits to replace with the transmit power controlinformation in the access request grant response message.
 16. The basestation of claim 14 wherein a number of timing advance bits to bereplaced is determined as a function of at least one from a group of: anaccuracy of a power delta for power control of the terminal device, acell radius of the base station.
 17. The base station of claim 14wherein the control processor replaces a number of timing advance bitswith a larger δ_(msg2) field in an uplink grant part of the accessrequest grant response.
 18. An integrated circuit for a base stationarranged to communicate with a terminal device on an uplink channel viaa relay device in a wireless communications system, the integratedcircuit comprising: a control processor arranged to: receive an accessrequest message from the terminal device; process the access requestmessage and extract a relayed control element that indicates relaydevice uplink assistance was used wherein the relayed control elementcomprises a power delta from the relay device; construct an accessrequest grant response message wherein the access request grant responsecomprises a larger field for power control and a comparable smallerfield for timing advance information for use in relayed communicationsas compared to corresponding size of fields for use in non-relayedcommunications; and transmit the access request grant response to theterminal device.
 19. A method for a base station arranged to communicatewith a terminal device on an uplink channel via a relay device in awireless communications system, the method comprising: receiving anaccess request message from the terminal device; processing the accessrequest message and extract a relayed control element that indicatesrelay device uplink assistance was used wherein the relayed controlelement comprises a power delta from the relay device; constructing anaccess request grant response message wherein the access request grantresponse comprises a larger field for power control and a comparablesmaller field for timing advance information for use in relayedcommunications as compared to corresponding size of fields for use innon-relayed communications; and transmitting the access request grantresponse to the terminal device.
 20. A non-transitory computer programproduct comprising executable program code to wirelessly communicatedata from a terminal device to a base station via a relay device, theexecutable program code operable for, when executed at the base station,performing the method of claim 19.